chem question

[superduper12]

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Question 1
The normality in acid of a 500 milliters aqeous solution of 1M sulfuric acid (H2SO4) is:

a. 1N
b. 2N
c. 3N
d. 8N

answer is B. normality is equivalents/ liters of solution.

I get 2equivalents/.5L = 4 N .....what am I missing here?

 

[superduper12]

Question 2

Do we assume the density of water remains constant (1g/cm3) despite different concentrations of solute dissolved? They used this in the ans below.

The molality of a 300 milliters of aqueous solution containing 33.3 grams of calcium chloride is:
a. 1m
b. 2m
c. 3m
d. 4m

ans is A. m = moles/ kilograms of solvent = .3 mol of CaCl2 / .3 kg of H20 = 1m

 

[superduper12]

question 3

Which is lower in energy in transition metal ions, the 3d orbitals or 4s orbitals.
Ans. 3d orbital.

I just learned earlier today that 4s are lower in energy that's why they fill before 3d. I know 4 is higher shell, but how would we know to answer through using the path of electron configuration or the shells alone?

 

[superduper12]

pure solids and liquids in equilibrium expression.

"The concentration of pure liquid or a pure solid is usually given a value of one for the equilibrium expression. Concentrations are only approximations for activities. Activities for pure solids and pure liquids are like 'effective' mole fractions. The mole fractions of a pure solid or liquid is one. Solvents are considered ideally dilute which means their mole fraction is one. The activity then of a pure solid or a liquid is approximately one. Be aware that pure solids and liquids can still participate in the equilibrium. When they do, they must be present in order for equilibrium to exist."

I know pure solids and liquids get 1 in the equilibrium expression, but I am not sure I understand why? If AB(solid) --> A+ (aq) + B- (aq)...as the reaction proceeds, we are increasing the amount of A+ and B-, and decreasing the amount of AB. If AB is decreasing, shouldn't it's mole fraction be less than 1??